Molecular Epidemiology of Oropouche Virus, Ceará State, Brazil, 2024

Abstract

During May-December 2024, we detected Oropouche virus (OROV) in 13.9% (263/1,890) of febrile patients in Ceará state, Brazil. Genomic sequencing revealed those cases were caused by a novel OROV reassortant previously identified in the Amazon region. Our data show the introduction and establishment of OROV transmission in Ceará, northeastern Brazil.

Keywords: Brazil; Oropouche fever; Oropouche virus; Peribunyaviridae; arbovirus; neglected tropical diseases; vector-borne infections; vector-borne orthobunyavirus; viruses.

Figure 1

Incidence of laboratory-confirmed Oropouche fever, dengue, and chikungunya cases in study of molecular epidemiology of OROV, Ceará state, Brazil, January–December 2024. Incidence is shown per epidemiologic week at state-level from epidemiologic week 1 (December 31, 2023–January 6, 2024) to epidemiologic week 52 of 2024 (December 22–28, 2024). CHIKV, chikungunya virus; DENV, dengue virus; OROV, Oropouche virus.

Figure 2

Geographic incidence of laboratory-confirmed Oropouche fever (A), dengue (B), and chikungunya virus (C), by municipality level, in study of molecular epidemiology of Oropouche virus, Ceará state, Brazil, January–December 2024.

Figure 3

Age–sex structure and clinical features of Oropouche fever cases in study of molecular epidemiology of OROV, Ceará state, Brazil, January–December 2024. A) Oropouche fever incidence based on the age–sex distribution of laboratory-confirmed cases. Dashed line indicates the cumulative incidence of 2.85/100,000 population in Ceará state. B) Signs and symptoms of OROV (n = 224) and DENV (n = 307) confirmed by quantitative reverse transcription PCR. DENV, dengue virus; OROV, Oropouche virus.

Figure 4

Phylogenetic analysis of the Oropouche virus (OROV) medium segment, 2023–2024 epidemic clade, in study of molecular epidemiology of OROV, Ceará state, Brazil, January–December 2024. The maximum-likelihood phylogenetic tree includes 420 representative OROV genomes from the 2023–2024 epidemic, with 22 newly sequenced genomes from Ceará (red dots highlighted in gray) generated in this study. Tip colors correspond to the state of origin for each sample. The phylogeny is midpoint-rooted for clarity. Scale bar represents the evolutionary distance in substitutions per nucleotide site. Bootstrap values, calculated from 1,000 replicates, are displayed at key nodes. GenBank accession numbers for all sequences used are described in the Appendix.